Carburetor



Oct. 5, 1965 w. s. KINGSLEY 3,210,055

CARBURETOR Filed July 7. 1961 4 Sheets-Sheet 2 7 T 76 a 0 IV? 85 MgggglL r "hell? Z W mzgyrozz.

ATTORNEY Oct. 5, 1965 w. G. KINGSLEY GARBURETOR 4Sheets-Sheet 3 FiledJuly 7. 1961 WI TNESS:

Em $73M;

ATTORNEY Oct. 5, 1965 w. G. KINGSLEY 3,210,055

CARBURETOR Filed July 7. 1961 4 Sheets-Sheet 4 INV EN TOR.

ATTORNEY United States Patent 3,210,055 CARBURETOR Warren G. Kingsley,Watkins Glen, N.Y., assrgnon to The Bendix Corporation, Elmira, N.Y., acorporation of Delaware Filed July 7, 1961, Ser. No. 122,462 9 Claims.(Cl. 261-39) The present invention relates to an improvement in acarburetor for an internal combustion engine and in general relates toan improvement in the air valve type of carburetor. More particularly,the invention relates to means for providing an enriched fuel-airmixture during predetermined periods of engine operation.

An air valve carburetor may include either a piston, poppet, butterfly,etc. type of valve that is responsive to air fiow and which is commonlyreferred to as an air valve. In the case of a piston type air valve thepiston is partially mounted in the body and a compartmentized chamberfor reciprocal movement in the mixture passage to provide anapproximately constant air velocity over fuel metering means. A taperedneedle carried by the piston projects into a fuel orifice disposed in abridge portion of a contoured restriction in the mixture passage toprovide the fuel metering means. Posterior of the contoured restriction,a throttle valve controls the introduction of the fuel-air mixture tothe engine manifolding. Piston movement to vary the air flow responsiveto throttle valve movements results from the pressure differentialsexisting between the pressure in a portion of the mixture passage and areference pressure usually atmospheric. The piston thus serves to varythe air flow in the mixture passage so as to maintain an approximatelyconstant air velocity and a substantially constant vacuum between theair valve, the bridge and the fuel metering means. The vacuum pressureexisting in the mixture passage between the bridge and throttle valve iscommunicated to the compartmentized chamber and will cause pistonmovements so as to vary the air flow and maintain the value of vacuumexerted on the fuel metering means at a substantially constant value.Since the needle valve is connected to the piston, any movement of thepiston will necessarily vary the needle-orifice restrictingcharacteristics by varying the effective orifice area and allowing agreater or lesser amount of fuel to be atomized.

Air valve carburetor construction, asheretofore used or proposed, hasone very definite limitation in that because of the use of the describedpiston-needle structure, it is impossible to enrich the fuel-air mixtureby restricting the air flow without concomitantly restricting the fuelmetering effect. It is, therefore, a primary object of the presentinvention to provide fuel enrichment means which overcomes theundesirable enrichment characteristics and limitations in the air valvecarburetor.

It is the object of the present invention to provide an enrichmentdevice for carburetors which is simple in construction, positive as wellas efiicient and reliable in operation, and inexpensive to manufactureand fabricate.

It is an object of the present invention to provide an enrichment devicefor air valve carburetors.

It is another object of the present invention to provide an enrichmentdevice for air valve carburetors which restricts the air flow betweenthe air valve and the bridge of the contoured restriction in the mixturepassage.

It is still another object of the present invention to provide anenrichment device which, during engine starting operation, willsequential-1y reduce the carburetor air flow and decrease therestriction in the fuel metering means to thereby enrich the fuel-airmixture supplied to the engine.

3,213,055 Patented Oct. 5, 1965 "ice It isa further object :ofthepresent invention to provide a device which, during wideeopen throttleoperation, will reduce the carburetor airflow-so as to obtainanincreased vacuum eifectand a greater. fuel flow from the meteringorifice thus enriching the'fuel-airmixture supplied to the engine.

It is afurthe-r object of the presentinvention to provide 'a contouredshaft .positioned transversely of a carburetor mixture passage adaptedidur'ingv normal'carburetoroperation not to alter the airflow'characteristics of the carburetor but adapted to be rotated duringpredetermined periods of engine operation1so as to vary thecarburetorair flowcharacteristicsandreduce the air flow.

It is a further object of the present invention to provide a contouredshaft positioned transversely :ofan air valve carburetor mixture passagewhich is adapted to'be rotated to sequentiallyreduce the air-flowbetween the air valve and apassage restriction .and to .displace the airvalve relative to the restriction so as to lessen the fuel meteringeffect.

"It isfurtherobject of the presentinvention to provide an enrichmentdevice for'airvalve carburetors which is motivated to its operativeposition by means responsive to engine temperatures.

It isa further object of the present invention to provide an enrichmentdevice for air valve carburetors which is motivated to its operativeposition by means responsive to predetermined engine .pressures.

It is a further object of the present invention to provide an enrichmentdevice for air valve carburetors which is motivated to its operativeposition by a combination thermostatically actuated member and a vacuummotor.

The invention further resides in certain novel features of construction,and combinations and arrangements of parts, and further objects andadvantages thereof will be apparent to those skilled in the art toWhichit pertains from the followingdescription of the preferred.iernbodiments thereof described with reference to the accompanyingdrawings in which similar reference characters representcorrespondingparts throughout the several views, and in which:

FIGURE 1 is a longitudinal sectional view taken on the plane of line 11of FIGURE 2 illustrating an air valve carburetor embodying the presentinvention and depicting the enrichment means inan inoperative position;

FIGURE 2-is anend elevation, partly broken away, of

anairvalvecarburetor embodying the present invention;

FIGURE 3 is a bottom view, partly broken away and in section,illustrating an air valve carburetor embodying the present invention;

FIGURE'4'is .a fragmentary detail perspective view, partly broken awayand in section, illustrating the mixture passage contoured restriction,the contoured enrichment member and the air valve as they operativelycombine to provide starting enrichment;

FIGURE 5 is a fragmentary view illustrating a thermostat member and avacuum motor in combination providing actuating means for a'contouredenrichment shaft;

FIGURE 6 is a fragmentary view illustrating the position of thecontoured enrichment shaft during normal carburetor operation;

FIGURE 7 isa fragmentary view-similiar to FIGURE 6 illustrating thecontouredenrichment shaft in its maximum enriching position;

FIGURE 8 is aview: similar toFIGURES illustrating motivating meansforenriching the fuel-airimixture when the engine operates 'at low manifoldvacuum;

FIGURE 9 is a schematic view illustrating an embodi- 11161111 formotivating the enrichment device; and

FIGURE 10 is a schematic view illustrating still another embodiment formotivating the enrichment device.

Referring now to the drawings and more particularly FIGURE 1, there isillustrated an air valve carburetor generally designated 11 consistingof a body 12, a cover assembly 13, and a fuel chamber 14. A mixturepassage 16 providing at its extremities an air intake 17 and a mixtureoutlet 18 is formed in the body 12. There is provided intermediate thepassage extremities, a contoured restriction 19 having inclined anteriorand posterior approaches 21 and 22, respectively, separated by asubstantially flat rectangular median portion 23 commonly referred to asa bridge. The contoured restriction 19 traverses only a segment of themixture passage 16 with the bridge portion 23 being substantiallyparallel to and spaced from the axis of the passage. A throttle valve 24in the mixture passage adjacent the outlet extremity 18 is supported onthe throttle shaft 26 jonrnalled in the body to control the introductionof the fuel-air mixture to the engine manifolding (not shown). Athrottle return spring 27 (FIGURE 3) anchored to one extremity of thethrottle shaft tends to maintain the throttle valve in a closed positionwhile linkage members generally designated 28 operable by the engineoperator control and limit the throttle valve opening and closingmovements.

The fuel chamber 14 depends from the body 12. Fuel is supplied to thefuel chamber through the inlet 29 (FIG- URE 3) and is controlled in anormal manner by a float actuated valve (not shown). Supported in acylindrical cavity 31 formed as a part of the body immediately below thebridge 23 is the fuel jet assembly generally indicated as 32. The jetassembly extends into the fuel chamber 14 and major portions of theassembly are surrounded by fuel.

The jet assembly 32 consists of a bushing 33 extending upwardly throughan aperture 34 centrally disposed in the bridge and opening into themixture passage. A bushing retaining screw 36 is threadedly received inthe cylinder 31 to maintain the bushing in contact with the under sideof thebridge. The bushing retaining screw 36 extends through anappropriately located opening 37 formed in the bottom of the fuelchamber 14 with an O ring 38 providing a sealing means therebetween. Atubular orifice member 39 slidably positioned in the bushing 33 extendsto the surface of the bridge to provide a metering orifice or jet. Themetering orifice is maintained in a proper positional relationshiprelative to the bridge surface by an orifice adjusting screw 41threadedly received in the bushing retaining screw and a spring 42compressively confined between a flange 43 on the orifice member 39 anda recess 44 formed in the bushing 33.

Fuel from the chamber 14 will flow through openings 46 in the bushingretainer 36, openings 47 in the orifice adjusting screw 41 and thencethrough the tubular orifice member 39 to the jet at the bridge in themixture passage. Metering of the fuel flow from the orifice willhereinafter be more fully described. Air entrapped in the jet assembly32 is vented through openings 48 in the bushing retainer 36 to the space49 between the bushing 33, the bushing retainer 36 and the cylinder 31and thence to an opening 51 communicating with the fuel chamber aboveits normal fuel level. In this manner vapor lock within the jet asemblyis effectively eliminated. A plug 52 closes the exterior opening of thebushing retaining screw 36.

Formed as a part of the body 12 and opening upwardly from the mixturepassage 16 is an inverted frustoconical structure 53 which combines withthe cover assembly 13 to define a compartmentized chamber generallydesignated as 54. Slidably supported within the chamber 54 and themixture passage 16 is a piston 56 commonly referred to as the air valve.The piston slidably engages in the opening 57 between the mixturepassage and the conical structure. The opening 57 is juxtaposed abovethe bridge 23. A flexible diaphragm 58 at its inner periphery is clampedbetween the piston 56 and a diaphragm retaining washer 59. The outerperiphery of A, the diaphragm is clamped between the mating flanges 61and 62 of the cover assembly 13 and the conical structure 53,respectively, thus dividing the chamber 54 into a suction chamber 63 anda reference pressure ohamber 64.

A piston shaft 66 press fitted into the piston extends upwardly throughthe piston cavity 67 into sliding engagement with the bushing 68 andguide member 69 formed in the ribbed cover 13 to accurately guide thepiston movements toward and away from the bridge. A light pistoncompression spring 71 confined between the cover 13 and the bottom wallof the piston cavity 67 urges the piston toward the bridge 23. Thepressure drop created by the air flow between the bridge and the base ofthe piston is communicated to the suction chamber 63 by openings 72formed in the base of the piston; thus the pressure existing in themixture passage 16 between the throttle valve 24 and the contouredrestriction 19 is communicated via the openings 72 and the piston cavity67 to the suction chamber 63. A reference pressure, usually atmosphericpressure, is communicated to the reference chamber 64 by a passage 73.This passage in the present embodiment is vented to the air entrancethrough the air filter means (not shown) to prevent the ingress ofundesirable foreign matter. The passage 73 may if desired be venteddirectly to the atmosphere, or into the air intake passage 17, oralternatively the passage may comprise a plurality of channels incombination communicating with two or more of the following, the airintake 17, the atmosphere, the mixture passage 16 adjacent the mixtureoutlet 18 or a source of manifold vacuum.

Operatively connected to the piston 56 is a tapered metering needle 74which projects into the fuel orifice 39 to regulate the effectiveorifice area subject to the substantially constant vacuum created by theconstant air velocity to restrict the fuel flow therefrom. The needle issecured to the piston by any convenient means such as a set screw 76.

Means in the form of punctiform detents 77, best illustrated in FIGURES2 and 3, are provided on the bottom face of the piston in a position tocontact the bridge and establish a minimal spatial Separation betweenthe piston 56 and the bridge 23. The function served by the detent 77could, of course, be accomplished by adjusting set screws (not shown)positioned in the body or conical structure adapted to engage the pistonduring its movement to establish the lower limits of piston travel.

Fuel enrichment means in the form of a contoured shaft 78, hereinafterfor convenience referred to as the choke shaft, is provided to enrichthe fuel-air mixture during predetermined periods of engine operation.The shaft 78 is journalled adjacent its extremities in the body 12 andtraverses the mixture passage substantially normal or crosswise to theair flow. The shaft intermediate its extremities is contoured as at 79.The contour in this embodiment is segmentally shaped and offset from theshaft axis. During normal carburetor operation, the contoured portion 79is positioned in a transverse void 81 formed in the incline 21. Thenormal non-enriching position of the contoured choke shaft relative tothe contoured restriction 19 is best illustrated in FIGURE 6 whileFIGURE 7 illustrates the contoured choke shaft rotated to its maximumenriching position. It will be apparent that during normal operation,illustrated in FIGURE 1, the shaft contour 79 is adapted to complementthe inclined surfaces adjacent the void 81 causing the contouredrestriction 19 to be substantially symmetrical. During enrichmentoperations, the contoured shaft is adapted to variably change the crosssection of the restriction 19 causing it to assume an asymmetricalconfiguration. Enrichment by rotation of the choke shaft in effectreduces the air flow between the piston 56 and the bridge 23.

When the piston 56 is fully actuatedv toward and in contact with thebridge 23, as at the time of starting,

the spatial separation therebetween will be at its minimum as determinedby the detents 77. Initial rotation of the shaft will cause the contour79 to move toward the base of the piston thereby progressively reducingthe air flow passage. Continued rotation of the choke shaft'after theair flow passage has been closed will cause the contour 79 to abut thepiston base and urge the piston away from the bridge while continuing toclose off the air passage. Movement of the piston introduced by theshaft will cause the metering needle to be withdrawn from the orificethus decreasing the fuel metering effect or, in other words, it willincrease the'eifective area of the jet. The reduction in metering effectduring enrichment is not accompanied by an increased air flow but,rather, the air flow is substantially decreased and the amount of fuelatomized is increased thereby providing a temporarily enriched mixture.

Enrichment at wide-open throttle can also be accomplished by means ofthe contoured choke shaft 79. At

wide-open throttle and during maximum r.p.m. or predetermined r.p.m.operations the piston will be drawn away from the bridge to the maximumamount allowable to provide the maximum air flow and the needle andorifice restriction will be reduced to its minimum providing thegreatest amount of effective jet area. Rotating the shaft contour 79willreduce the air flow passage While the fuel metering means remainunaffected thus an enriched fuel-air mixture is readily obtainable tosupplement normal wide-open throttle at maximum or predetermined r.p.m.operation. In effect, more fuel is atomized into less air. At Wide-openthrottle below the maximum or predetermined r.p.m. operations the airvalve will assume various positions less than the full open or upposition. Rotating the shaft contour 79 will act to reduce the air flowbetween the air valve and bridge 19 while the fuel metering means remainat least temporarily unaffected thus causing an enriched fuel-airmixture.

The contoured shaft 78 can be actuated or motivated in several ways.Linkage, generally indicated as 82, may be manually actuated by theengine'operator through a Bowden wire connect-ion (not shown). Thislinkage can be mechanically coupled to the throttle linkage 28 so as toprovide a predetermined throttle setting prior to enrichment. A chokereturn spring'83 will urge the contoured choke shaft to itsnon-enriching position. Mechanical linkages well known to those skilledin this art will'serve the express purpose without requiring theexercise of inventive ingenuity.

The enrichment means may be automatically controlled. In FIGURE 5 thereis illustrated an embodiment of the invention for obtaining coldstarting enrichment wherein the choke shaft 178 having a contouredportion 179, has an extremity 181 extending into a housing 182. Athermostatically actuated member 183 in the form of a bimetallic coilspring is anchored to the shaft extremity 181 and to a fixed member in afashion well known in this art. The coil 183 is adapted when cold toactuate 'the choke shaft 178 to an enriching position and when heated toactuate the shaft to a non-enriching position. Heat generated by theengine is communicated to the housing 182 in any convenient manner tocause the coil to be actuated responsive to changes in enginetemperatures. A vacuum motor in the form of a piston 184, slidablymounted in a portion of the housing 182 and connected to a source ofvacuum, is operably connected to the shaft extremity 181 to vary andcontrol the enriching position of the shaft dependent upon varyingengine operating conditions. While the embodiment of FIGURE 5 has beendescribed and illustrated as being a parallel connection, i.e., thebimetallic coil and vacuum motor are connected to the choke shaftstructurally independent of each other, it will be apparent to thoseskilled in the art that a series connection would work equally as well,i.e., that the'bimetallic coil is anchored to the shaft at one end andthe other end is connected to the vacuum motor.

In FIGURE 9 there is diagrammatically illustrated an embodiment forautomatically enriching the mixture. A bimetallic coil spring 301 isanchored at one extremity to a stationary member and has its freeextremity adapted to cooperate with a lever 302 secured to a choke shaft303. Biasing means such as a spring 304 associated with the lever causethe choke to be rotated in a counterclockwise direction to an enrichingposition. Means generally designated as 306, consisting of either avacuum motor or solenoid, are operably connected to the lever 302 andoffset the biasing action of the spring 304 for the purposes wellunderstood in this art. As the engine attains proper operatingtemperatures the free extremity of the bimetallic spring 301 will engagethe lever 302 and urge the choke 303 in a clockwise direction to itsnon-enriching position indicated in broken lines.

In FIGURE 10 there is diagrammatically illustrated still anotherembodiment for automatically enriching the mixture. A lever 321 isfixedly secured to a choke shaft 322. A bimetallic spring 323, hereillustrated as a hairpin spring has its extremities operably connectedto the lever 321 and a connecting member 324 of means generallydesignated as 326, consisting of either a vacuum motor or solenoid. Whenthe utilizing engine is started, the elements will be positioned as isindicated by the solid lines. After the engine has been initiallyactuated the means 326 will cause the bimetallic spring 323 and lever toassume the position illustrated in broken lines so as to preventover-enrichment. As the engine attains its operating temperature thebimetallic spring 323 will contract causing the lever 321 to assume theposition illustrated in dash lines which position is the chokenonenriching position.

In FIGURE 8 there is illustrated an embodiment of the invention whereinthe contoured shaft 278 is actuated to provide an enriched mixture atwide-open throttle operation. A cylindrical housing 281 formed as a parton or of the body 12 supports a piston 282 adapted for reciprocalmovement toward and away from a cylinder end wall 283. Passage means 284communicate a source of engine manifold vacuum to the cylindricalhousing adjacent its end Wall 283. A metering restriction 286 may beprovided. Rod means 287 connect the piston to a lever 288 fixedlysecured to the extremity of the choke shaft 278 to translate thereciprocal piston movements into rotarial movements of the shaft 278. Aspring 289 encompassing the shaft extremity biases the shaft lever tothe enriched position illustrated in broken lines and acts against theforce of the manifold vacuum. Stop means 291 and 292 limit shaftrotation. Manifold vacuum communicated to the housing 281 normallyexerts sufiicient force on the piston to draw it toward the end wall 283and maintain the shaft in a normal nonenriching position. At wide-openthrottle the manifold vacuum will be insufiicient to overcome the forceof the spring 289 and the shaft will be rotated to its enrichingposition. Alsov at the initiation of starting operations the shaft willassume an enriching position. In the enriching position the shaft willreduce the air flow between the bridge and the air valve. The meteringneedle and orifice at wide-open operation will assume a predeterminedrelationship. When the air How is reduced by the choke shaft, theneedle-orifice relationship will not be immediately changed and thus thereduced air flow unaccompanied by any change in the fuel metering effectwill resultingly provide an enriched fuel-air mixture over and abovethat obtainable at normal wide open throttle operation.

In operation, variations in the degree of throttle valve opening betweenfully closed and wide open will vary the mixture passage pressuresexisting between the bridge 23 and the throttle valve 24. The passagepressures are communicated to the upper chamber 63 of thecompartmentized chamber 54 via the openings 72 and piston cavity 67.Atmospheric pressure in the reference chamher establishes a pressuredifferential in the chamber 54 with a resulting degree of movement inthe air valve 56 depending on the differential and the degree ofcompression of the piston spring 71. The air valve movements will beautomatic over the entire range of throttle operation and will provide asubstantially constant air velocity between the base of the air valve 56and the bridge 23. This constant air velocity passing over the orifice39 creates a substantially constant vacuum on the orifice or jet. Sincethe tapered metering needle 74 is operatively connected to the piston56, movements of the piston away from and toward the bridge willnecessarily increase or decrease the effective area of the orifice 39exposed to the constant vacuum.

At the time of starting, the piston will be biased by the spring 71 intoengagement with the bridge 23 with the detents 77 allowing only aminimal separation to exist therebetween. Initially the mixture passagepressure posterior of the piston is insufiicient to cause the piston tobe actuated to provide a greater fuel metering effect and to, in turn,provide an enriched fuel-air mixture needed to initiate engineoperation. Actually, piston movement necessary to obtain a decreasedmetering effect would be undesirable since it would also increase theamount of air and the fuel-air mixture would not be enriched as desired.By the use of interconnected throttle valve linkages 28 and choke shaftlinkages 82, the contour '79 of the shaft 78 can be positioned in anenriching position after a predetermined degree of throttle opening. Thechoke shaft will be rotated and sequentially the shaft contour 79 willclose off or reduce the air flow over the bridge and displace the pistonrelative to the bridge thereby withdrawing the tapered needle andenlarging the eifective area of the orifice 39. Choke shaft rotationwill effectively reduce or vary the air flow and increase the fuelmetered into the mixture passage to provide the enriched startingmixture. The contoured choke can be actuated by means of athermostatically actuated spring 183 and a vacuum motor 184 asillustrated in FIGURE 5. The spring 183 is sensitive to enginetemperatures and when the engine is cold the spring will actuate thechoke shaft 178 to an enriched position comparable to that in FIGURE 7whereby the air flow between the bridge and piston is restricted and thepiston is displaced a predetermined amount to increase the effectivefuel metering area. Hot air from the engine is communicated to thethermostatic element housing 182. As an engine becomes heated, thespring releases its biasing force allowing the choke shaft to be biasedby the choke return spring 83 to a normal non-enriching position.Additionally, after the engine has become operative, engine pressure istransferred to the vacuum motor 184. The vacuum motor 184 exerts offorce on the shaft 178 tending to overcome the bias of the thermostaticspring and to motivate the choke shaft toward its normal nonenrichingposition.

In the embodiment illustrated in FIGURE 8 the choke shaft 278 is biasedby the spring 289 to its enriching position. Manifold vacuumcommunicated to the cylindrical housing 281 via the passage 284.Manifold vacuum below a predetermined value will exert a force on avacuum motor piston 282 of sufiicient magnitude to actuate the chokeshaft to its normal non-enriching position. When the engine is operatedat full load or wide-open throttle, the manifold vacuum will beinsufiicient to overcome the bias of spring 289 and the choke shaft willbe rotated by a spring to its enriching position. In the enrichingposition the air flow between the air valve 56 and the bridge 23 will berestricted without a change in metering relationship between the taperedneedle 74 and the fuel orifice 39. The resulting fuel-air mixture willbe enriched above that normally obtainable at wide-open throttle. Itwill be apparent to those skilled in the art that rotation of the chokeshaft 278 for enri hment would not be as great as that schematicallyillustrated in FIGURE 7 since full rotation would provide an enrichedmixture which is too rich for the normal running power mixture. Sincethe embodiment illustrated in FIGURE 8 is intended to provide enrichmentonly at full load or wide-open throttle operation and not primarily forstarting enrichment, then the degree of choke shaft rotation can belimited by the engagement of the lever 288 with the stop or limiting pin292. If the embodiment of FIGURE 8 were intended to provide startingenrichment then a choke actuating lever could be utilized which wouldact as the modulating means within a predetermined intermediate degreeof rotation and suitable overrun means could provide full chokeoperation.

It is to be understood that the invention is not limited in itsapplication to details of construction and arrangement of partsillustrated in the accompanying drawings since the invention is capableof other embodiments and of being practiced or carried out in variousways. It is also to be understood that the phraseology or terminologyemployed is for the purpose of description and not of limitation, and itis not intended to limit the invention herein claimed beyond therequirements of the prior art.

I claim:

1. A carburetor for an internal combustion engine comprising:

a body provided with a mixture passage, said passage providing an airintake and a mixture outlet;

a fuel orifice opening into the passage;

means communicating with the orifice for supplying fuel to the orifice;

air valve means for restricting the air flow in the passage;

metering means operably connected to the air valve and cooperating withthe orifice for restricting and regulating the fuel discharge into theair flow from the orifice;

throttle valve means in the passage for controlling the introduction ofa fuel-air mixture to the engine; and,

means including a shaft supported in the passage for reducing the airflow;

means responsive to engine temperatures connected to said shaft formoving said shaft in response to temperature variation.

2. A carburetor as set forth in claim 1 wherein:

the air valve comprises a piston supported by the body and operativelyextending into the passage, means mounting said piston for reciprocalmovement toward and away from the fuel orifice; and,

the means for reducing air flow in the passage comprises a shaft memberadapted upon rotation to reduce the air flow through the passage, saidshaft being journalled in the body and having a contoured portion offsetfrom the axis of said shaft.

3 A carburetor for an internal combustion engine comprising:

a body provided with a mixture passage, said passage providing an airintake and a mixture outlet;

a contoured restriction formed within the passage providing a bridge;

a fuel orifice in the bridge;

means communicating with the orifice for supplying fuel thereto;

a piston air valve, means mounting said piston for movement toward andaway from the bridge for restricting the air flow in the passage;

metering means operably connected to the piston and cooperating with theorifice for restricting and regulating the fuel discharge from theorifice;

a throttle valve in the passage for controlling the introduction of afuel-air mixture to the engine;

a contoured shaft journalled in the body traversing the passage adjacentthe bridge adapted for movement during predetermined engine operatingconditions to reduce the air flow for enriching the mixture during saidpredetermined engine operating conditions; and, means for actuating thecontoured shaft.

4. A carburetor as set forth in claim 3 wherein the means for actuatingsaid contoured shaft comprises linkage means interconnected between saidshaft and said throttle valve for obtaining shaft rotation atpredetermined throttle valve positions.

5. A carburetor as set forth in claim 3 wherein:

the contoured shaft extremities are journalled in the body and theintermediate portion thereof is segmentally shaped and offset from theaxis of said shaft to provide the contour; and,

means are provided for defining a minimum air passage between the bridgeand the piston when the piston approaches the bridge.

6. A carburetor as set forth in claim 5 wherein the contouredrestriction comprises a flat median portion and inclined approachesleading to and from said flat median portion, said median portionproviding said bridge, one of said approaches being formed with a voidcrosswise of said passage; said contoured shaft being positioned in saidvoid.

7. An air valve carburetor for internal combustion engines comprising:

a body provided with a mixture passage, said body being adapted forconnection between an air intake and engine manifolding;

a contoured restriction formed in the passage further comprising:

a flat median portion providing a bridge;

inclined anterior and posterior approaches leading to and away from thebridge, one of said approaches being formed with a void transverse ofthe passage;

a fuel orifice in the bridge;

means communicating within the orifice for supplying fuel thereto;

a piston supported by the body and operably extending into the passageand means for mounting said piston for reciprocal movement toward andaway from the bridge;

means responsive to pressure diiferentials for actuating the piston;

metering needle means carried by the piston adapted to project into theorifice for varying the fuel discharge therefrom;

throttle valve means supported in the passage posterior 0f the contouredrestriction for controlling the introduction of a fuel-air mixture tothe engine manifolding;

means for enriching the fuel-air mixture during predetermined engineoperating conditions, said enriching means further comprising a shaftrotatably supported in the body and including a contoured portion, saidshaft being positioned in the void of the contoured restriction; and

means for actuating the enriching means.

8. An air valve carburetor as set forth in claim 7 further comprising:

detent means on the piston adapted to engage the bridge for defining aminimum air passage between the piston and the bridge when the enrichingmeans is inoperative.

9. A carburetor for an internal combustion engine comprising:

a body provided with a mixture passage, said passage providing an airintake and a mixture outlet;

21 fuel orifice opening into the passage;

means communicating with the orifice for supplying fuel to the orifice;

air valve means for restricting the air flow in the passage;

metering means operably connected to the air valve and cooperating withthe orifice for restricting and regulating the fuel discharge into theair flow from the orifice;

means including a shaft in the passage for reducing the air flow; and

means responsive to engine pressure, connected to said shaft for movingsaid shaft in response to pressure variation.

References Cited by the Examiner UNITED STATES PATENTS 1,822,712 9/31Skimmer 26l44 2,062,496 12/36 Brokel 261-52 2,195,867 4/40 Mallory 26l522,523,798 9/50 Winkler 26l50 FOREIGN PATENTS 595,815 7/25 France.300,725 11/28 Great Britain.

HARRY B. THORNTON, Primary Examiner.

HERBERT L. MARTIN, Examiner.

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING: A BODYPROVIDED WITH A MIXTURE PASSAGE, SAID PASSAGE PROVIDING AN AIR INTAKEAND A MIXTURE OUTLET; A FUEL ORIFICE OPENING INTO THE PASSAGE; MEANSCOMMUNICATING WITH THE ORIFICE FOR SUPPLYING FUEL TO THE ORIFICE; AIRVALVE MEANS FOR RESTRICTING THE AIR FLOW IN THE PASSAGE; METERING MEANSOPERABLY CONNECTED TO THE AIR VALVE AND COOPERATING WITH THE ORIFICE FORRESTRICTING AND REGULATING THE FUEL DISCHARGE INTO THE AIR FLOW FROM THEORIFICE;